Idle isn't quite right, Blah. Options

[corsepervita]

Intrake leaks will result in a high idle, not a low one. Unplug the air temp sensor in the intake plenum and see if that helps. Pull and hold a vacuum on the MPS. Check the hose to the MPS. Adjust the valves, tight valves can cause a low idle speed. Check and set the point dwell. Set the timing, hoses off and plugged. Check the fuel pressure while the engine is running. 29 PSI is the goal. Report back.

The Cap'n

Alright... so here we go... I finally got some time today to work on this.

Hose to the MPS is new. MPS is also a rebuilt unit (replaced the previously bad MPS I had). Although the numbers are not the same. However, car idles the same with bad MPS or new rebuilt MPS.

MPS will hold vacuum with no issues.

Valves were adjusted to spec less than 1000 miles ago, car ran more smoothly but idle did not change.

Dwell is set and is at a happy 47.

Timing set to 27btdc.

Do not have equipment to test psi, however, I pulled plugs and the mixture is LEAN. Not RICH like I thought previously.

After setting the timing, the idle was still funky. I decided to disconnect the hose for timing retard and suddenly..... the idle became normal and the car would actually react to the idle air screw and the car could be set to 800rpm idle.

(IMG:style_emoticons/default/WTF.gif)

Now, regarding Cabinet Maker's previous post... I went ahead and pulled the sensor and indeed, the resistance was where I found it earlier when things were "kind of warm" - I guess I did not wait long enough because after I took the car for a long drive, the resistance was about 50-70ohms, not 2200.

I went ahead and heated up the spare sensor I have with a heat gun and sure enough, it also went below 100ohms as it should.

I emailed Jim (Previous owner "Porsche Rescue") and he confirmed that he replaced the sensor when he gave me the description of the sensor he replaced.

So at this point I am leaning less towards mixture and more towards timing or something else. The plugs weren't ridiculously lean, just a tad on the lean side. With the previous MPS it was so rich the car would load up and just die. It will remain idling, but when hot, will pop a bit if you give it gas just barely at very low rpms. If you let off the gas at higher rpms you get a decel pop pop pop which if I am reading correctly is indeed a "lean thing"...

So I guess I was reading into this improperly.

I appreciate everyone's help.

At this point I can at least confirm:

- Car is LEAN, not rich, as previously thought
- Idle smooths out and will actually react to idle air screw when dizzy retard is disconnected, if it is hooked back up, the idle turns to crap and the car runs terribly again.
- Sensor for CHT is within spec when previously thought it was not, is under 100ohms at running temp

I haven't fixed it yet, but damnit I'm tired and I want a beer. (IMG:style_emoticons/default/beer3.gif)

PS: Part # off my MPS is 0 280 100 049

[r_towle]

Mismatched mps units to ecu units can cause issues.

Check this table to make sure you are set correctly with what you have.

http://members.rennlist.com/pbanders/djetp...m#Compatibility

[corsepervita]

Yep, correct MPS.

Although I have wonderful news! I found my issue. I kind of forgot to unplug the vacuum lines when I set my timing sooooooooo it was off, a lot.

I just went and set the timing and hooked it back up, set the idle and it runs like a freaking champ. Super smooth, idle like butter (as buttery as they can anyway) and it runs and drives predictably. No more hiccups, no more decel popping (I heard ONE pop the entire drive). It even started right up.

So you guys can put this one down on PEBKAC, ID10T or whichever one of those you most prefer since it was all user error on my end. Gee whiz, timing makes a difference?

I will inspect the plugs tomorrow to see if the condition of them changes any. I actually found that I am already running B6ES and NOT BP6ES plugs as I previously thought, so after taking them out I went... "OHHHHHH."

So now I have more plugs for next time around.

Anyway, HAPPY 914 owner right here!

[r_towle]

Congrats and I am happy it was a simple error versus more money out of your pocket.

Now, drive it like you stole it before it gets out of tune again...which it will

[TheCabinetmaker]

(IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/piratenanner.gif) (IMG:style_emoticons/default/smilie_pokal.gif) Glad ya got figured out, and good job on the diagnosis.

The only tune you really need to keep a regular eye on is dwell. Keep it happy at 47. timing should stay the same. Remember, dwell affects timing. I check my valves at least every 5K, and dwell about every 1K just for the heck of it.

[corsepervita]

(IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/piratenanner.gif) (IMG:style_emoticons/default/smilie_pokal.gif) Glad ya got figured out, and good job on the diagnosis.

The only tune you really need to keep a regular eye on is dwell. Keep it happy at 47. timing should stay the same. Remember, dwell affects timing. I check my valves at least every 5K, and dwell about every 1K just for the heck of it.

Yeah, it ran "okay" when I first got it but the idle was never perfect. It did the stuttering low idle when I first got it and never really was stable. I finally decided to just completely go through it and also do gaskets and points and what not. Night and day!

I appreciate all the help and support here. This is the first "older" car I've ever owned. All of my cars of course are older than me. My 911, my 924 cars and the 914. The 914 is the oldest, however.

I have a strange addiction to Porsche cars and the 914 is just a time machine for me, I love it, and love working on it. I'm slowly starting to understand it better.

I seem to be a bit on the advanced side with the timing. I did get some pinging this morning while driving it around, only at around 3k rpms and only under load. So I will back it off "a hair" and see how that helps. I eyeballed the timing last night but no doubt is a huge difference over setting it with vacuum attached LOL!

What I really need to do is make one of those pelicanparts templates and mark the 27btdc mark on the impeller so I can make it spot on.

Thank you again for all the patience and assistance. I know many of you have been doing this stuff since these cars came out. I'm still a "young'n" in comparison.